You can get matting at a farm supply store for pretty cheap. I also found it at Wal-mart for dirt cheap. That's what I use. it has interlocking pieces, and you can stack it 3-4 high if need be.

Farm supply store, only things I've ever seen for sale up here for farms is feed and such; most of the goods go directly from the supplier to the island's farm that requires it via the carrier and they'd order in bulk and have business accounts etc...but, I'll certainly keep my ears open just in case.

It's complicated here one minute we're part of the UK, the next we're not, depending on suppliers